Internet Protocol Television (IPTV) services are based on broadband IP networks and mainly focus on streaming media. Compared with conventional TV, IPTV can support more abundant and flexible services, provide a comprehensive IPTV value-added service platform, and realize services such as communication, data, video, and audio. Data generated by a source is needed to be sent to a plurality of destination nodes in live television/broadcast television (LTV/BTV) services among the IPTV, that is, a point-to-multipoint communication. Currently, the solution to point-to-multipoint communication is a multicast technology that can effectively utilize the network bandwidth and avoid waste of bandwidth resources.
In order to support the multicast technology, a Resource and Admission Control Subsystem (RACS) architecture is proposed, and it is described in detail in Telecommunication and Internet converged Services and Protocols for Advanced Networking (TISPAN).
By implementing resource admission control, the RACS hides details of the transport network from the service layer, supports the separation of service control and transport functions, and gets to know the resource usage condition of the transport network, so as to ensure the correct and proper use of resources of the transport network, thus ensuring the Quality of Service (QoS) of the service and preventing the bandwidth and service from being embezzled. FIG. 1 shows functional architecture of an RACS. The main network elements in the figure are introduced as follows.
A service-based policy decision function (SPDF) provides a universal interface to the application layer, hides the underlying network topology and specific access type, and provides service-based policy control. The SPDF selects a local policy according to a request of an Application Function (AF), maps the request into Internet Protocol Quality of Service (IPQOS) parameters, and sends the parameters to an Access-Resource and Admission Control Function (A-RACF) and a Border Gateway Function (BGF), so as to request for corresponding resources.
The A-RACF is located in an access network and has admission control and network policy convergence functions. The A-RACF receives a request from the SPDF, and then realizes admission control according to a stored policy, thus accepting or refusing the request for transport resources. The A-RACF obtains network attachment information and user QoS list information from a Network Attachment Sub-System (NASS) via an e4 reference point. Accordingly, available network resources can be determined according to network location information (for example, a physical node address of an access user). Meanwhile, the user QoS list information is referred to when a resource allocation request is processed.
The transport layer contains three types of functional entities. Among them, BGF is a border gateway, which can be located between the access network and the core network (for realizing functions of a core border gateway) and can also be located between two core networks (for realizing functions of an Internet border gateway). Under the control of SPDF, BGF completes Network Address Translation (NAT), gating, QoS label, bandwidth restriction, measurement and resource synchronization functions. A Resource Control Enforcement Function (RCEF) implements the Layer 2/Layer 3 (L2/L3) media stream policy defined by an access operator that is sent via a Re reference point by A-RACF to accomplish gating, QoS label, bandwidth restriction and other functions. A Layer 2 Termination Function (L2TF) is a functional entity terminating the Layer 2 connection in the access network. The RCEF and L2TF are different functional entities, and are generally realized together on a physical equipment, IP Edge.
In addition, in the latest draft for RACS R2, a new function, i.e., Core-RACF (C-RACF) is defined, which is located in the core network for performing resource admission control.
For ease of the subsequent description given to the control of multicast bearer resources, the bearer layer network is divided into three segments: access network, access converged network, and core network, as shown in FIG. 2. The segment between user equipment (UE) and an admission control policy enforcement node (may be an AN or IP Edge) is referred to as the access network. The segment between this node and a core border node is referred to as the access converged network. The segment beyond the core border node is referred to as the core network segment. The SPDF returns a final resource authorization result to the AF.
The inventor found during research and application that IPTV multicast services have currently been operated in traditional networks, but the effective control of multicast bearer resources has not been realized in the RACS architecture.